On a full frame length certain focal lengths (from what I've read, 70-100) are the ideal for a 'flattering' and realistic impression of a human face as a human eye sees it. Too short and it's distorted, too long and it's flattened.

How does this range translate to m43? Theory is fine but also has anyone done any experimentation?

85mm seems to be the "classic" focal length for portraits. With the 2x sensor crop of M4/3 cameras, that translates to 42.5mm.

Luckily for us, there are two 42.5mm lenses… the currently shipping and splendid (!) all-manual Voigtländer 42.5mm f0.95 and the upcoming AF Panasonic 42.5mm f1.2.

I've had my Voigtländer 42.5mm for several weeks, and was lucky enough to get it just before taking it on a 2-week trip along the French and Italian Mediterranean coast. I must say it's an absolutely beautiful lens, that seems even better than the other native M4/3 f0.95 Voigtländers, the 17.5mm and 25mm.